uk landscapes - rivers

Question 1

what is the long profile and what are the sections?

Answer 1

a long profile shows the gradient of a river as it journeys from source to mouth.
upper course -> middle course -> lower course

Question 2

what is a river cross profile and how does this change?

Answer 2

a cross-profile is a section taken sideways across a river channel and or a valley.
it changes downstream becuase of vertical and lateral erosion.

Question 3

give 3 processes of erosion

Answer 3

-hydraulic action-water is forced into cracks and the trapped air cant escape under the pressure so the rock cracks,
-abrasions/corrasaion-boulders andd rocks scratch and scraper the walls and floor
-solution-dissolving of rocks such as chalk
-attrition-smooths out rocks in the river

Question 4

give 3 processes of river transportation

Answer 4

-solution-minerals are dissolved in the water and carried downstream
-suspension- fine light material is held up and carried downstream
-saltation-small pebbles and stones are bounced along the river bed.
-traction-large boulders and rocks are rolled along the river bed-bedload.

Question 5

define source

Answer 5

original point from which the river flows

Question 6

define mouth

Answer 6

the place where the river flows into a larger body of water such as the sea

Question 7

define confluence

Answer 7

the point at which two rivers or streams join

Question 8

define tributary

Answer 8

a stream or smaller river which joins a larger stream or river.

Question 9

define watershed

Answer 9

the edge of highland surrounding a drainage basin. it marks the boundary between two drainage basins.

Question 10

difference between vertical and lateral erosion?

Answer 10

lateral erosion- sideways erosion by a river on the outside of a meander channel. it eventually leads to the widening of the valley and contributes to the formation of the flood plain.

vertical erosion-downwards erosion of a river bed

Question 11

explain how a v-shaped valley forms

Answer 11

in the upper course, the river erodes its bed by hydraulic and abrasive action. this is dominantly vertical erosion which creates steep slopes on either sides of the river that weathered material can fall down. the rock is then removed by transportation which leaves steep v-shaped sides to the valley.

Question 12

explain how a waterfall is formed

Answer 12

-a waterfall forms where there is a junction between a hard rock and a soft rock.
-it erodes the soft rock and not the hard rock, which leaves a lip between the rocks.
-this lip deepens are the soft rock further erodes through hydraulic action.
-splash back causes hydraulic action to weaken the rock behind the waterfall.
-pieces of soft rock brake off and contribute to abrasion, which forms a plunge pool at the bottom of the waterfall.
-continued undercutting causes the hard rock to loose support and break off.

Question 13

how does a gorge form?

Answer 13

a gorge forms because of a retreating waterfall, which leaves a channel thats been eroded out of the soft rock.

Question 14

explain how a meander forms(helicoidal flow, erosion, deposition)

Answer 14

water starts off travelling faster in deeper sections and slower in shallower sections, which sets off helicoidal flow that corkscrews from one bank to the other.
-fast flowing water on the outside bank causes more lateral erosion, and slower flowing water on the inside bank causes more deposition.
-this creates a slip-off slope on the inside bank and a river cliff on the outside bank.
-this slowly pushes the meander further out.

Question 15

explain how a floodplain forms

Answer 15

a floodplain forms when repeated flooding creates a wide valley around the river.
a levee is formed becuase the heaviest sediment settles close to the rive in a flood. as the sediment builds up over many floods, it builds up a bank on either side of the river.

Question 16

explain how an estuary forms.

Answer 16

a flood plain in the lower course of the river is permanently flooded becuase of rising sea levels. the original channel is now surrounded by mud flats(formed by the sea meeting the river increasing deposition) and the estuary.

Question 17

what is a flood hydrograph?

Answer 17

a hydrograph shows how a river’s discharge changes in response to a precipitation event.

Question 18

how can human factors affect flood risk and how will they affect the hydrograph

Answer 18

physical factors like deforestation and urbanisation decrease the infiltration rate and so there is less lag time and a higher risk of flooding and more water making it to the rivers quickly.

Question 19

how can physical factors affect flood risk?

Answer 19

factors like the rock type and relief can change the rate of infiltration and surface run off becuase water infiltrates faster on different types of rock or different gradients of slopes.

Question 20

what is hard engineering (what are the positives and negatives)

Answer 20

hard engineering uses heavy machinery to build artificial structures which work against nature to reduce the risk of floodding.
pos: can provide hydroelectric power as well as preventing flooding effectively
neg: expensive

Question 21

what is soft engineering( give a good and bad thing about it)

Answer 21

soft engineering involves adapting to a river and learning to live with it.
pos:cheaper
neg:less effective

Question 22

give an example of flood management- what did they do and how effective was it

Answer 22

Kielder Dam-hard engineering
they built a dam to flood the river valley higher up and then let the water through in a more controlled way. highly effective against floods- virtually no risks